Zoom lens

ABSTRACT

A zoom lens comprises a first lens group having a positive refracting power, a second lens group having a negative refracting power, and a third lens group having a positive refracting power, disposed in the named order from the object side, wherein the first lens group has a 1-1 lens group having a negative refracting power and a 1-2 lens group having a positive refracting power, disposed in the named order from the object side, wherein zooming from a wide angle end to a telephoto end is effected by increasing a gap between the first lens group and the second lens group and reducing a gap between the second lens group the third lens group, while fixing the first lens group, wherein focusing from infinity to near is effected by moving the 1-1 lens group to the object side; and 
     wherein the following condition is satisfied: 
     
         0.5&lt;f1/fw&lt;2.0, 
    
     where fw is a focal length of the total system when an object at infinity is in focus at the wide angle; and 
     and f1 is a focal length of the first lens group when the object at infinity is in focus.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a zoom lens for a single lens reflex camera, and particularly to a zoom lens which is capable of effecting focusing from infinity to extreme near at any zoom position.

2. Related Background Art

Conventionally, there is provided for a single lens reflex camera a so-called macro lens which is capable of focusing from infinity to extreme near distance with image magnification of about -0.5 to -1.

Also, there is provided a kind of zoom lens which additionally has a function capable of photographing with a shorter distance than an ordinary closest object distance, which is called a macro mechanism.

Or, there is provided a close-up lens which is attached to the object side of the photographing lens, in order to reduce the closest object distance.

However, either of the conventional macro lenses is a single focus lens, which requires an operation for changing a distance between an object to be photographed and the camera and, simultaneously, an operation for focusing, in order to change an image magnification. For this reason, it is troublesome to alter a photo composition when using a tripod for photographing an object at a close distance.

Also, a most part of the macro mechanism of a zoom lens can be used only at either one of the wide angle end (so-called wide macro) or the telephoto end (so-called tele macro), so that zooming can not be carried out at macro photographing. As a result, the operability of such lens is equal to or worse than that of a macro lens with a single focus. Moreover, the maximum image magnification of such lens is -0.3 or around, which is not sufficient when an object is to be photographed as a larger image.

Though some type of the macro mechanism of zoom lens allows close photographing at all zoom positions, the maximum image magnification in this case is -0.25 or around, which is also not sufficient when an object is desired to be photographed as a larger image.

When accessories such as a close-up lens and the like is used, such accessories are to be attached or detached, depending on whether an object to be photographed is at a far distance or a close distance, which is troublesome.

SUMMARY OF THE INVENTION

Accordingly, an object of the present invention is to provide a zoom lens capable of extreme close photographing suitable for a single lens reflex camera, in which zooming can be carried out at any object distance from infinity to closest without deviation of the image plane, with the maximum image magnification of about -0.75 to -1 or around and a zoom ratio of 2 or more, an excellent image performance and a sufficient amount of light at marginal area can be obtained in every photographing condition.

Focusing methods for the zoom lens include, in addition to a method of moving a first lens group, an inner focus method and a rear focus method. However, the inner focus method or the rear focus method has a problem that the position of an image plane deviates when zooming is carried out while a near object is focused. Further, since it is required to arrange a space for moving the focusing lens in an optical path, then the extreme close photographing is carried out, and a movement amount of the focusing lens is large, the zoom lens becomes large-sized inevitably.

Also, according to the focusing method for moving the first lens group, a refracting power of the first lens group may be positive in one case and negative in the other.

When the refracting power of the first lens group is positive, an angle of the oblique chief ray (the ray passing through the center of the stop) exits from the first lens group and the optical axis is larger than an angle of the oblique chief ray enters the first lens group and the optical axis, as shown in FIG. 1A. Accordingly, when the first lens group is moved to the direction of the object for focusing, a necessary effective diameter of the first lens group is extremely increased.

On the other hand, when the refracting power of the first lens group is negative, an angle of the oblique chief ray (the ray passing through the center of the stop) exits from the first lens group and the optical axis is smaller than an angle of the oblique chief ray enters the first lens group and the optical axis, as shown in FIG. 1B. Accordingly, the necessary effective diameter of the first lens group is not so much increased even when the first lens group is moved to the direction of the object for focusing.

For this reason, when a movement amount of the first lens group becomes large for performing an extreme close photographing, it is desirable that the refracting power of the first lens group should be negative.

However, according to a zoom lens in which the refracting power of the first lens group is negative, the total length of the zoom lens is liable to be large with respect to a focal length of the zoom lens. Therefore, when the first lens group having a negative refracting power is employed in such zoom lens having a larger focal length, the total length of the lens system becomes further larger, which is not practical in some cases.

When a macro photographing which is aimed by the present invention is conducted, a larger working distance (distance from an object to be photographed to the tip end of the zoom lens) is practically advantageous. In order to secure a sufficient working distance, a larger focus length is desirable.

Then, the zoom lens capable of extreme close photography of the present invention is arranged, as shown in FIG. 1C, in such a manner that the refracting power of the first lens group is positive so as to reduce the total length of the lens system and secure the working distance simultaneously, the first lens group is composed of a negative 1-1 lens group and a positive 1-2 lens group, and only the 1-1 lens group is moved to the object direction so as to effect focusing.

There are some kind of zoom lenses in which the first lens group is moved for zooming and another in which the first lens group is not moved for zooming. With a zoom lens in which the first lens is moved for zooming, when the zooming is performed at extreme close focusing state, a distance from the object to the tip end of the zoom lens is changed, and the image plane deviates. Then, in the zoom lens capable of extreme close photography of the present invention, the first lens group is arranged to be fixed in zooming.

The present invention is to realize a zoom lens suitable for obtaining a comparatively large focal length by using a first lens group having the above-mentioned characteristics. More specifically, the present invention provides a zoom lens which has a first lens group having a positive refracting power, a second lens group having a negative refracting power and a third lens group having a positive refracting power in the named order from the object, wherein the first lens group has a 1-1 lens group having a negative refracting power and a 1-2 lens group having a positive refracting power in the named order from the object side, zooming from a wide angle end to a telephoto end is effected by enlarging a gap between the first lens group and the second lens group and reducing a gap between the second lens group and the third lens group while fixing the first lens group, focusing from infinity to near is effected by moving the 1-1 lens group to the object direction, and the following condition is satisfied when fw is a focal length of the total system in a state that an object at infinity is focused at the wide angle end, and f1 is a focal length of the first lens group in a state that the object at infinity is focused:

    0.5<f1/fw<2.0                                              (1).

The condition (1) presents an appropriate range for the focal length of the first lens group in a state that an object at infinity is focused. Above the upper limit of the condition (1), the total length of the zoom lens becomes larger. Conversely, below the lower limit of the condition (1), the positive refracting power of the 1-2 lens group when the first lens group is divided into the negative 1-1 lens group and the positive 1-2 lens group becomes large so that a spherical aberration and a chromatic aberration generated in the 1-2 lens group increase undesirably.

In the present invention, it is preferable when f₁₋₁ is the focal length of the 1-1 lens group, the following condition should be satisfied:

    0.5<|f.sub.1-1 /fw|<2.0                  (2).

The condition (2) presents an appropriate range for the focal length of the 1-1 lens group. Above the upper limit of the condition (2), a movement amount of the 1-1 lens group required for focusing is increased so that the total length of the zoom lens becomes larger. Conversely, below the lower limit of the condition (2), the negative refracting power of the 1-1 lens group becomes great and the positive refracting power of the 1-2 lens group is also increased so that it is difficult to correct aberrations including a spherical aberration and a chromatic aberration, and further fluctuations in the aberrations in focusing are increased.

Also, in the present invention, it is preferable when f₁₋₂ is the focal length of the 1-2 lens group, the following condition should be satisfied:

    0.25<f.sub.1-2 /fw<1.5                                     (3).

The condition (3) presents an appropriate range for the focal length of the 1-2 lens group. Above the upper limit of the condition (3), the total length of the zoom lens becomes larger. Conversely, below the lower limit of the condition (3), the positive refracting power of the 1-2 lens group becomes great so that it is difficult to correct the spherical aberration and the chromatic aberration.

Also, in the present invention, it is preferable when Z2 is β2T /β2W, Z3 is β3T /β3W, β2T is an imaging magnification of the second lens group at an telephoto end, β2W is an imaging magnification of the second lens group at a wide angle end, β3T is an imaging magnification of the third lens group at the telephoto end, and β3W is an imaging magnification of the third lens group at the wide angle end, the following condition should be satisfied:

    0.6<Z2/Z3<2.0                                              (4).

The condition (4) presents an appropriate range for a variable magnification effect ratio to be born by the second and third lens groups. Above the upper limit of the condition (4), the magnification change effect born by the second lens group becomes large so that fluctuations in the aberrations in zooming are increased. Conversely, below the lower limit of the condition (4), the magnification change effect of the third lens group becomes larger so that it is difficult to maintain the total length of the zoom lens to be the same and it is also difficult to make the f-number of the lens at the telephoto end fast.

Also, in the present invention, it is preferable when f2 is the focal length of the second lens group, the following condition should be satisfied:

    0.25<|f2/f1|<0.7                         (5).

The condition (5) presents an appropriate range for the focal length of the second lens group. Below the lower limit of the condition (5), the refracting power of the second lens group becomes greater and fluctuations in the aberrations in zooming are increased. Conversely, above the upper limit of the condition (5), the variable magnification change effect of the second lens group becomes smaller so that it is difficult to obtain a high zoom ratio.

Also, in the present invention, the third lens group may be fixed or may be moved to the object side or the image side so long that a gap between the second lens group and the third lens group can be reduced in zooming. However, It is preferable for making ratio of the variable magnification effect born by the second lens group and the third lens group to be appropriate that the third lens group should be disposed as being movable and is moved in such a manner that the position of the third lens group at the telephoto end is closer to the object than the position at the wide angle end.

Note that a gap which is changeable in zooming may be arranged amid the second lens group or the third lens group so as to correct fluctuations in the aberrations in zooming more satisfactorily.

Moreover, in order to achieve the above object, according to the present invention, there is provided a zoom lens capable of extreme close photographing, which comprise a first lens group G1 having a positive refracting power and at least two lens groups disposed on the image side of the first lens group G1, in which the focal length of the total lens system is varied by changing at least two air gaps between the lens groups, the first lens group G1 has a 1-1 lens group G11 with a negative refracting power and a 1-2 lens group G12 with a positive refracting power in the named order from the object, focusing is effected from an object at infinity to an object at a close distance by moving the 1-1 lens group G11 to the object side, and the following condition is satisfied when the focal length of the 1-1 lens group G11 is f11 and the focal length of the total lens system in an infinite in-focus state at the wide angle end is fw:

    0.8<|f11|/fw<1.6.

According to a preferable arrangement of the present invention, the 1-1 lens group G11 comprises a front group GF having a positive refracting power and a rear group GR having a negative refracting power in the named order from the object, and the following condition is satisfied when a focal length of the front group GF is fF and the focal length of the 1-1 lens group G11 is f11:

    0.9<fF/|f11|<1.9.

For zoom lenses, the focusing method of moving the first lens group located closest to the object side when an object at a close distance is focused is generally employed. However, when the first lens group has a positive refracting power, if trial is made to effect focusing from infinity to an extreme close object distance by this method, the necessary effective diameter of the first lens group is extremely increased to be unpractical.

Therefore, the present invention employs an arrangement that the first lens group G1 with the positive refracting power has the 1-1 lens group G11 with the negative refracting power and the 1-2 lens group G12 with the positive refracting power, and focusing of an object at a close distance is effected by moving only the 1-1 lens group G11 with the negative refracting power to the object side.

In such an arrangement of the present invention, the following condition (6) is satisfied when f11 is the focal length of the 1-1 lens group G11, and fw is the focal length of the total lens system in an infinite in-focus state at the wide angle end, in order to suppress fluctuations in the aberrations caused by focusing and to reduce a movement amount (focusing moving amount) of the 1-1 lens group G11 for effecting focusing:

    0.8<|f11|/fw<1.6                         (6).

The condition (6) stipulates an appropriate range for the focal length of the 1-1 lens group G11.

Above the upper limit of the condition (6), the focusing movement amount of the 1-1 lens group G11 becomes large and the total lens length (a distance between the lens surface closest to the object and the image surface along the optical axis) is increased.

Conversely, below the lower limit of the condition (6), the negative refracting power of the 1-1 lens group G11 increases and the positive refracting power of the 1-2 lens group G12 also increases. As a result, it becomes difficult to correct aberrations including a spherical aberration or a chromatic aberration, and further the fluctuations in the aberrations caused by focusing increase.

Also, if the present invention employs an arrangement that the 1-1 lens group G11 has the front group GF with the positive refracting power and the rear group GR with the negative refracting power in the named order from the object side, it is effective for reducing the total length of the lens, and decreasing the effective diameter of the first lens group G1, and it is further effective for reducing a fluctuation in a spherical aberration and coma caused by focusing. Further, in this case, it is preferable when fF is the focal length of the front group GF, to satisfy the following condition (7):

    0.9<fF/|f11<1.9                                   (7).

The condition (7) stipulates an appropriate range for the focal length of the front lens group GF in the 1-1 lens group G11.

Above the upper limit of the condition (7), the positive refracting power of the front group GF becomes smaller, so that it is difficult to reduce the total length of the lens and the effective diameter of the first lens group G1. Further, a fluctuation in a spherical aberration and that in a coma caused by focusing become undesirably excessive in this case.

Conversely, below the lower limit of the condition (7), the positive refracting power of the front group GF increases and, together with this, the negative refracting power of the rear group GR also increases. As a result, it is necessary to increase the number of constituent lenses of the front group GF and that of the rear group GR in order to correct aberrations generated in the front group GF and the rear group GR, which is undesirable.

Further, in order to correct aberrations or suppress fluctuations in the spherical aberration and the coma caused by focusing, it is desirable that the front group GF should comprise a negative meniscus lens being convex on the object side and a biconvex lens in the named order from the object side. It is also desirable that the rear group GR should comprise a negative lens having a surface with a larger curvature on the image side, a negative lens having a surface with a larger curvature on the object side, and a positive lens with a larger curvature on the object side in the named order from the object side.

Also, in the present invention, it is desirable that the following conditions (8) and (9) should be satisfied:

    R'/ft<4                                                    (8),

and

    ft'/ft<0.7                                                 (9),

where R' is an axial distance between the object and the image surface when the image magnification at the telephoto end is -0.5, ft is the focal length of the entire lens system in an infinite in-focus state at the telephoto end, and ft' is the focal length of the entire lens system when the image magnification at the telephoto end is -0.5. Note that the axial distance is a distance along the optical axis.

If the conditions (8) and (9) are satisfied, the focal length of the entire lens system is reduced when the 1-1 lens group G11 is moved to the object side at the telephoto end to focus an object at a close distance, whereby the closest object distance can be extremely short.

Also, in the present invention, it is desirable to satisfy the following condition (10):

    1.05<TL'/TL<1.4                                            (10),

where TL is an axial distance between the surface closest to the object and the image surface in an infinite in-focus state at the telephoto end, and TL' is an axial distance between the surface closest to the object and the image surface when the image magnification at the telephoto end is -0.5.

Above the upper limit of the condition (10), a change in the total length of the lens caused by focusing becomes large, and it becomes undesirably difficult to simplify the constitution of a lens barrel.

Conversely, below the lower limit of the condition (10), a change in the image magnification per unit movement amount of the 1-1 lens group G11, which serves as a focusing lens group, becomes larger so that a higher precision is required for positioning the focusing lens group. For this reason, focusing with a higher precision becomes undesirably difficult both in manual focusing and auto focusing.

In addition, according to the present invention, there is provided a zoom lens which comprises a first lens group G1 having a negative refracting power, a second lens group G2 having a positive refracting power, a third lens group G3 having a negative refracting power, and a fourth lens group G4 having a positive refracting power disposed in the named order from the object side, wherein the focal length is changed from a wide angle end to a telephone end by changing an air gap between the first lens group G1 and the second lens group G2, increasing an air gap between the second lens group G2 and the third lens group G2, and reducing an air gap between the third lens group G3 and the fourth lens group G4, and the following conditions are satisfied when the focal length of the first lens group G1 is f1, the focal length of the entire system at the wide angle end is fw, the axial air gap between the first lens group G1 and the second lens group G2 in a infinity photographing state at the wide angle end is D12W:

    0.8<|f1|/fw<1.6;

and

    D12W/fw<0.1.

According to a preferable arrangement of the present invention, the first lens group G1 is fixed or the second lens group G2 is fixed during zooming.

Also, it is preferable to satisfy the following condition when a distance between a position of the first lens group G1 at which it is closest to the image surface and a position of the first lens group G1 at which it is farthest from the image surface along the optical axis is Δ1, and the focal length of the entire system at the wide angle end is fw:

    Δ1/fw<0.1.

Also, according to the present invention, in order to prevent the necessary effective diameter of the first lens group from increasing, there are provided the first lens group G1 having the negative refracting power, the second lens group G2 having the positive refracting power, the third lens group G3 having the negative refracting power, and the fourth lens group G4 having the positive refracting power disposed in the named order from the object side. Then, zooming from the wide angle end to the telephoto end by changing the air gap between the first lens group G1 and the second lens group G2, increasing the air gap between the second lens group G2 and the third lens group G3, and reducing the air gap between the third lens group G3 and the fourth lens group G4. With such arrangement of the present invention, it is rendered possible to reduce the effective diameter of the first lens group G1.

According to the present invention, in addition to the above-mentioned arrangements, the following conditions (11) and (12) are satisfied:

    0.8<|f1|/fw<1.6                          (11),

and

    D12W/fw<0.1                                                (12),

where fw is the focal length of the total system at the wide angle end, f1 is the focal length of the first lens group G1, the D12W is the axial air gap between the first lens group and the second lens group G2 in an infinity photographing state at the wide angle end.

The condition (11) relates to the focal length of the first lens group G1. The condition (11) stipulates a condition for making the focusing movement amount to be proper when focusing is effected by the first lens group G1 and for reducing fluctuations in the aberrations caused by the focusing.

Above the upper limit of the condition (11), the refracting power of the first lens group G1 is reduced and the focusing movement amount of the first lens group G1 is increased. As a result, a focusing mechanism of the lens barrel becomes bulky or complicated.

Conversely, below the lower limit of the condition (11), the refracting power of the first lens group G1 is increased and fluctuations in the aberrations including a spherical aberration caused by focusing are increased.

The condition (12) relates to the air gap between the first lens group G1 and the second lens group G2 at the wide angle end, and stipulates a condition for reducing the necessary effective diameter of the first lens group G1.

Above the upper limit of the condition (12), the air gap between the first lens group G1 and the second lens group G2 is increased so that the first lens group G1 becomes extremely larger than the second lens group G2. Further, since the photographing is conducted at an extreme close distance, the necessary effective diameter for the first lens group G1 becomes further larger.

Also, according to the present invention, it is desirable to fix the first lens group G1 or the second lens group G2 during zooming in order to simplify the barrel structure.

Incidentally, a zoom lens, in which the first lens group is largely moved during zooming, is characterized in that an image position is changed when zooming is effected in a state that an object at a close distance is focused, which is a serious problem when extreme close photographing is to be conducted. For this reason, it is most preferable to fix the fist lens group G1 during zooming. In this case, the image position is not changed even when zooming is conducted in a state that an object at a close position is focused.

Also, in the present invention, it is preferable to satisfy the following condition (13) when Δ1 is a distance along the optical axis between a position of the first lens group G1 at which it is closest to the image surface and a position of the first lens group G1 at which it is farthest from the image surface during zooming:

    Δ1/fw<0.1                                            (13).

When the first lens group G1 is moved during zooming, if the condition (13) is satisfied, a change of the position of the first lens group G1 caused by zooming is small so that it is possible to reduce a change of the image position even if zooming is conducted when an object at a close distance is focused.

Also, in order to secure a large zoom ratio (a ratio between the focal length at the telephoto end and that at the wide angle end) in the above-mentioned lens constitution, it is preferable to move the third lens group G3 to the image side and the fourth lens group G4 to the object side during zooming from the wide angle end to the telephoto end. Note that a ratio between a movement amount for zooming of the third lens group G3 and that of the fourth lens group G4 may be fixed during zooming, or may be varied according to zooming. If the ratio of a movement amount for zooming is fixed during zooming, the lens barrel constitution can be simplified. Also, if the ratio of the movement amount for zooming is varied according to zooming, fluctuations in the aberrations caused by zooming can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A to 1C are schematic drawings to explain an effect of the present invention;

FIG. 2 is a lens constitution drawing according to a first embodiment of the present invention;

FIGS. 3A to 3D are drawings to show aberrations at a wide angle end in an infinity photographing state according to the first embodiment;

FIGS. 4A to 4D are drawings to show aberrations at an intermediate focal length in the infinity photographing state according to the first embodiment;

FIGS. 5A to 5D are drawings to show aberrations at the telephoto end in the infinity photographing state according to the first embodiment;

FIGS. 6A to 6D are drawings to show aberrations at the wide angle end in a extreme close photographing state according to the first embodiment;

FIGS. 7A to 7D are drawings to show aberrations at the intermediate focal length in the extreme close photographing state according to the first embodiment;

FIGS. 8A to 8D are drawings to show aberrations at the telephoto end in the extreme close photographing state according to the first embodiment;

FIG. 9 is a lens constitution drawing according to a second embodiment of the present invention;

FIGS. 10A to 10D are drawings to show aberrations at the wide angle end in the infinity photographing state according to the second embodiment;

FIGS. 11A to 11D are drawings to show aberrations at the intermediate focal length in the infinity photographing state according to the second embodiment;

FIGS. 12A to 12D are drawings to show aberrations at the telephoto end in the infinity photographing state according to the second embodiment;

FIGS. 13A to 13D are drawings to show aberrations at the wide angle end in a state of extreme close photography according to the second embodiment;

FIGS. 14A to 14D are drawings to show aberrations at the intermediate focal length in the extreme close photographing state according to the second embodiment;

FIGS. 15A to 15D are drawings to show aberrations at the telephoto end in the extreme close photographing state according to the second embodiment;

FIG. 16 is a lens constitution drawing according to a third embodiment of the present invention;

FIGS. 17A to 17D are drawings to show aberrations at the wide angle end in a state of infinity photography according to the third embodiment;

FIGS. 18A to 18D are drawings to show aberrations at the intermediate focal length in the infinity photographing state according to the third embodiment;

FIGS. 19A to 19D are drawings to show aberrations at the telephoto end in the infinity photographing state according to the third embodiment;

FIGS. 20A to 20D are drawings to show aberrations at the wide angle end in the extreme close photographing state according to the third embodiment;

FIGS. 21A to 21D are drawings to show aberrations at the intermediate focal length in the extreme close photographing state according to the third embodiment;

FIGS. 22A to 22D are drawings to show aberrations at the telephoto end in the extreme close photographing state according to the third embodiment;

FIG. 23 is a drawing to show the constitution of a zoom lens according to fourth and fifth embodiments of the present invention;

FIGS. 24A to 24E are drawings to show aberrations at the wide angle end in the infinity photographing state according to the fourth embodiment;

FIGS. 25A to 25E are drawings to show aberrations at the intermediate focal length in the infinity photographing state according to the fourth embodiment;

FIGS. 26A to 26E are drawings to show aberrations at the telephoto end in the infinity photographing state according to the fourth embodiment;

FIGS. 27A to 27E are drawings to show aberrations at the wide angle end in the extreme close photographing state according to the fourth embodiment;

FIGS. 28A to 28E are drawings to show aberrations at the intermediate focal length in the extreme close photographing state according to the fourth embodiment;

FIGS. 29A to 29E are drawings to show aberrations at the telephoto end in the extreme close photographing state according to the fourth embodiment;

FIGS. 30A to 30E are drawings to show aberrations at the wide angle end in the infinity photographing state according to the fifth embodiment;

FIGS. 31A to 31E are drawings to show aberrations at the intermediate focal length in the infinity photographing state according to the fifth embodiment;

FIGS. 32A to 32E are drawings to show aberrations at the telephoto end in the infinity photographing state according to the fifth embodiment;

FIGS. 33A to 33E are drawings to show aberrations at the wide angle end in the extreme close photographing state according to the fifth embodiment;

FIGS. 34A to 34E are drawings to show aberrations at the intermediate focal length in the extreme close photographing state according to the fifth embodiment;

FIGS. 35A to 35E are drawings to show aberrations at the telephoto end in the extreme close photographing state according to the fifth embodiment;

FIG. 36 is a drawing to show the constitution of a zoom lens according to a sixth embodiment of the present invention;

FIGS. 37A to 37E are drawings to show aberrations at the wide angle end in the infinity photographing state according to the sixth embodiment;

FIGS. 38A to 38E are drawings to show aberrations at the intermediate focal length in the infinity photographing state according to the sixth embodiment;

FIGS. 39A to 39E are drawings to show aberrations at the telephoto end in the infinity photographing state according to the sixth embodiment;

FIGS. 40A to 40E are drawings to show aberrations at the wide angle end in the extreme close photographing state according to the sixth embodiment;

FIGS. 41A to 41E are drawings to show aberrations at the intermediate focal length in the extreme close photographing state according to the sixth embodiment;

FIGS. 42A to 42E are drawings to show aberrations at the telephoto end in the extreme close photographing state according to the sixth embodiment;

FIG. 43 is a drawing to show the constitution of a zoom lens according to a seventh embodiment of the present invention;

FIGS. 44A to 44E are drawings to show aberrations at the wide angle end in the infinity photographing state according to the seventh embodiment;

FIGS. 45A to 45E are drawings to show aberrations at the intermediate focal length in the infinity photographing state according to the seventh embodiment;

FIGS. 46A to 46E are drawings to show aberrations at the telephoto end in a the infinity photographing state according to the seventh embodiment;

FIGS. 47A to 47E are drawings to show aberrations at the wide angle end in the extreme close photographing state according to the seventh embodiment;

FIGS. 48A to 48E are drawings to show aberrations at the intermediate focal length in the extreme close photographing state according to the seventh embodiment;

FIGS. 49A to 49E are drawings to show aberrations at the telephoto end in the extreme close photographing state according to the seventh embodiment;

FIG. 50 is a drawing to show the constitution of a zoom lens according to an eighth embodiment of the present invention;

FIGS. 51A to 51E are drawings to show aberrations at the wide angle end in the infinity photographing state according to the eighth embodiment;

FIGS. 52A to 52E are drawings to show aberrations at the intermediate focal length in the infinity photographing state according to the eighth embodiment;

FIGS. 53A to 53E are drawings to show aberrations at the telephoto end in the infinity photographing state according to the eighth embodiment;

FIGS. 54A to 54E are drawings to show aberrations at the wide angle end in the extreme close photographing state according to the eighth embodiment;

FIGS. 55A to 55E are drawings to show aberrations at the intermediate focal length in the extreme close photographing state according to the eighth embodiment; and

FIGS. 56A to 56E are drawings to show aberrations at the telephoto end in the extreme close photographing state according to the eighth embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will be described below. FIGS. 2, 9 and 16 respectively show lens constitutions according to the first, second and third embodiments. In either of the embodiments, there are provided a first lens group G1 having a positive refracting power, a second lens group G2 having a negative refracting power, and a third lens group G3 having a positive refracting power, disposed in the named order from the object side, in which the first lens group G1 has a 1-1 lens group G1-1 having a negative refracting power and a 1-2 lens group G1-2 having a positive refracting power in the named order from the object side.

Zooming from a wide angle end to a telephoto end is effected by enlarging a gap between the first lens group G1 and the second lens group G2 and reducing a gap between the second lens group G2 and the third lens group G3, in a state that the first lens group G1 is fixed. Also, focusing from infinity to near is effected by moving the 1-1 lens group G1-1 to the object direction.

Tables 1, 2 and 3 below respectively show specific values of the first, second and third embodiments. In the "Total System Specific Values", f represents a focal length, F an f-number, and 2ωa field angle. In the "Lens Specific Values", the first column includes lens surface numbers in the order from the object side, γ in the second column represents a radius of curvature of lens surface, d in the third column a lens surface separation, ν in the fourth column an Abbe's number which is a value for a d-line (λ=587.6 nm), n in the fifth column a refractive index for the d-line, and the sixth column includes the lens group numbers. In the "Lens Specific Values" and the "Zooming Data", B.f. represents a back focus. In the "Zooming Data for Extreme close Photographing", β represents a photographing magnification.

In the following Table 4, values for parameters in each of the conditions for each of the embodiments.

                  TABLE 1                                                          ______________________________________                                          Total System Specific Values!                                                 ______________________________________                                         f = 82.40˜105.00˜194.00                                            F/4.00                                                                         2ω = 28.8˜22.5˜12.3°                                  ______________________________________                                          Lens Specific Values!                                                               r          d       ν    n                                             ______________________________________                                          1    91.5689    2.5000  23.01   1.86074                                                                              G.sub.1-1                                2    54.6088    4.4623                                                         3    125.2484   8.1078  25.50   1.80458                                                                              G.sub.1-1                                4    -114.3868  1.4036                                                         5    -717.9812  1.8000  57.53   1.67025                                                                              G.sub.1-1                                6    64.8899    11.9531                                                        7    -48.2282   1.8000  53.93   1.71300                                                                              G.sub.1-1                                8    -181.7976  0.1000                                                         9    132.4360   4.4439  50.19   1.72000                                                                              G.sub.1-1                               10    959.6726   d.sub.10                                                      11    225.8299   6.6705  46.54   1.80411                                                                              G.sub.1-2                               12    -142.4932  0.1000                                                        13    194.7697   1.8000  23.01   1.86074                                                                              G.sub.1-2                               14    65.8071    8.4092  82.52   1.49782                                                                              G.sub.1-2                               15    -855.2567  0.1000                                                        16    64.2082    7.0404  82.52   1.49782                                                                              G.sub.1-2                               17    355.4772   0.1000                                                        18    108.6708   4.4253  82.52   1.49782                                                                              G.sub.1-2                               19    406.2827   d.sub.19                                                      20    -182.2134  1.8000  44.69   1.80218                                                                              G.sub.2                                 21    34.7719    6.3571  23.01   1.86074                                                                              G.sub.2                                 22    133.7423   2.8713                                                        23    -137.7067  1.8000  46.54   1.80411                                                                              G.sub.2                                 24    99.1954    d.sub.24                                                      25    Stop       1.0000                                                        26    119.4745   5.2877  47.07   1.67003                                                                              G.sub.3                                 27    -127.0264  0.1000                                                        28    54.4238    8.8922  70.41   1.48749                                                                              G.sub.3                                 29    -71.2730   1.8000  23.01   1.86074                                                                              G.sub.3                                 30    293.7445   0.1000                                                        31    30.8625    9.4426  64.10   1.51680                                                                              G.sub.3                                 32    698.0400   0.1000                                                        33    29.5818    1.8000  46.54   1.80411                                                                              G.sub.3                                 34    22.8055    16.6395                                                       35    332.0543   3.7213  23.01   1.86074                                                                              G.sub.3                                 36    -65.3245   2.6640                                                        37    -28.3332   1.8000  46.54   1.80411                                                                              G.sub.3                                 38    28.8409    5.8422  35.51   1.59507                                                                              G.sub.3                                 39    -168.7423  B.f.                                                          ______________________________________                                                 Wide angle    Intermediate                                                                             Telephoto                                              end           position  end                                            ______________________________________                                          Zooming data for infinity photographing!                                      f       82.3993       104.9989  193.9946                                       d.sub.10                                                                               2.0000        2.0000    2.0000                                         d.sub.19                                                                               3.3315        14.1165   22.4546                                        d.sub.24                                                                               42.4152       32.3130   3.8086                                         B.f.    50.0184       49.3354   69.4997                                         Zooming data for extreme close photographing!                                 (Photographing distance R = 361.000)                                           β  -0.4247       -0.5411   -0.9998                                        d.sub.10                                                                               53.5369       53.5369   53.5361                                        d.sub.19                                                                               3.3315        14.1165   22.4546                                        d.sub.24                                                                               42.4152       32.3130   3.8086                                         B.f     50.0184       49.3354   69.4997                                        ______________________________________                                    

                  TABLE 2                                                          ______________________________________                                          Total system specific values!                                                 ______________________________________                                         f = 103.00˜180.00˜291.00                                           F/4.42˜4.87˜5.75                                                   2ω = 22.9˜13.2˜8.3°                                   ______________________________________                                          Lens specific values!                                                               r          d       ν    n                                             ______________________________________                                          1    202.3833   2.5000  23.01   1.86074                                                                              G.sub.1-1                                2    74.7234    2.0616                                                         3    103.7676   10.1010 28.19   1.74000                                                                              G.sub.1-1                                4    -117.3133  8.5700                                                         5    -416.6663  1.8000  57.53   1.67025                                                                              G.sub.1-1                                6    100.7133   9.3818                                                         7    -54.6651   1.8000  53.93   1.71300                                                                              G.sub.1-1                                8    -786.3826  0.1000                                                         9    204.0600   3.3528  23.01   1.86074                                                                              G.sub.1-1                               10    892.5335   d.sub.10                                                      11    227.4791   6.6286  46.54   1.80411                                                                              G.sub.1-2                               12    -130.5874  0.1000                                                        13    127.5199   1.8000  23.01   1.86074                                                                              G.sub.1-2                               14    56.3193    9.8744  82.52   1.49782                                                                              G.sub.1-2                               15    -331.0902  0.1000                                                        16    144.6848   4.4213  82.52   1.49782                                                                              G.sub.1-2                               17    7715.2325  0.1000                                                        18    113.8541   4.6776  82.52   1.49782                                                                              G.sub.1-2                               19    1014.1073  d.sub.19                                                      20    -270.8368  1.8000  39.61   1.80454                                                                              G.sub.2                                 21    28.8260    6.5396  23.01   1.86074                                                                              G.sub.2                                 22    90.5561    3.7961                                                        23    -88.4184   1.8000  46.54   1.80411                                                                              G.sub.2                                 24    391.6283   d.sub.24                                                      25    Stop       1.0000                                                        26    119.7663   4.6332  45.00   1.74400                                                                              G.sub.3                                 27    -148.0246  0.1000                                                        28    54.6985    7.7566  70.41   1.48749                                                                              G.sub.3                                 29    -63.6645   1.8000  23.01   1.86074                                                                              G.sub.3                                 30    437.2122   0.1000                                                        31    27.3174    7.7335  51.66   1.52944                                                                              G.sub.3                                 32    401.5286   2.1415                                                        33    65.8655    1.8000  46.54   1.80411                                                                              G.sub.3                                 34    28.8881    18.7121                                                       35    129.1625   4.0621  25.48   1.73038                                                                              G.sub.3                                 36    -50.1532   1.6282                                                        37    -26.5763   1.8000  46.54   1.80411                                                                              G.sub.3                                 38    25.0964    5.7247  35.51   1.59507                                                                              G.sub.3                                 39    -158.4348  B.f.                                                          ______________________________________                                                 Wide angle    Intermediate                                                                             Telephoto                                              end           position  end                                            ______________________________________                                          Zooming data for infinity photographing!                                      f       103.0000      180.0000  291.0003                                       d.sub.10                                                                               2.0000        2.0000    2.0000                                         d.sub.19                                                                               2.8628        20.3587   27.8294                                        d.sub.24                                                                               54.7331       28.0038   2.4114                                         B.f.    64.1501       73.3835   91.5054                                         Zooming data for extreme close photographing!                                 (Photographing distance R = 456.500)                                           β  -0.3539       -0.6185   -0.9999                                        d.sub.10                                                                               36.3604       36.3604   36.3604                                        d.sub.19                                                                               2.8628        20.3587   27.8294                                        d.sub.24                                                                               54.7331       28.0038   2.4114                                         B.f     64.1501       73.3835   91.5054                                        ______________________________________                                    

                  TABLE 3                                                          ______________________________________                                          Total system specific values!                                                 f = 70.00˜105.00˜140.00                                            F/4.64˜4.91˜5.48                                                   2ω = 35.0˜22.9˜17.1°                                  ______________________________________                                          Lens specific values!                                                                r        d          ν n                                              ______________________________________                                          1     82.6447  2.0000     49.45                                                                               1.77279 G.sub.1-1                               2     36.9605  8.6887                                                          3     -138.6274                                                                               1.8000     60.03                                                                               1.64000 G.sub.1-1                               4     151.8914 2.6551                                                          5     61.5613  4.7043     25.50                                                                               1.80458 G.sub.1-1                               6     167.3722 d.sub.6                                                         7     74.5810  5.2300     60.03                                                                               1.64000 G.sub.1-2                               8     -422.1466                                                                               0.1000                                                          9     65.5006  1.8000     25.80                                                                               1.78472 G.sub.1-2                              10     29.2835  7.6202     60.03                                                                               1.64000 G.sub.1-2                              11     195.1004 0.2000                                                         12     59.9530  3.5978     70.41                                                                               1.48749 G.sub.1-2                              13     143.2392 d.sub.13                                                       14     537.9466 1.4000     39.61                                                                               1.80454 G.sub.2                                15     18.8956  6.8087     25.50                                                                               1.80458 G.sub.2                                16     242.2438 4.2297                                                         17     -81.0401 1.4000     33.89                                                                               1.80384 G.sub.2                                18     64.1056  d.sub.18                                                       19     Stop     1.0000                                                         20     38.3674  3.9686     49.45                                                                               1.77279 G.sub.3                                21     -155.0001                                                                               2.2159                                                         22     51.6311  4.7267     64.10                                                                               1.51680 G.sub.3                                23     -30.1463 1.4000     28.56                                                                               1.79504 G.sub.3                                24     22.2304  0.1172                                                         25     21.8052  4.9612     70.41                                                                               1.48749 G.sub.3                                26     -135.3967                                                                               5.0107                                                         27     48.0149  4.7230     23.01                                                                               1.86074 G.sub.3                                28     -47.6948 4.2264                                                         29     -32.3971 1.4000     46.54                                                                               1.80411 G.sub.3                                30     37.9077  B.f.                                                           ______________________________________                                         Wide angle        Intermediate                                                                             Telephoto                                          end               position  end                                                ______________________________________                                          zooming data for infinity photographing!                                      f      70.0000        105.0000  140.0000                                       d.sub.6                                                                               2.0000         2.0000    2.0000                                         d.sub.13                                                                              2.5929         15.2800   18.7705                                        d.sub.18                                                                              32.1834        15.2340   2.8260                                         B.f.   55.1376        59.3998   68.3173                                         Zooming data for extreme close distance!                                      (Photographing distance R = 283.900)                                           β -0.5003        -0.7504   -1.0005                                        d.sub.6                                                                               56.0923        56.0923   56.0923                                        d.sub.13                                                                              2.5929         15.2800   18.7705                                        d.sub.18                                                                              32.1834        15.2340   2.8260                                         B.f    55.1376        59.3998   68.3173                                        ______________________________________                                    

                  TABLE 4                                                          ______________________________________                                         embodiment No.                                                                             1            2      3                                              ______________________________________                                         (1) f.sub.1 /f.sub.w                                                                       1.138        1.041  1.305                                          (2) |f.sub.1-1 /f.sub.W |                                                1.214        0.971  1.243                                          (3) f.sub.1-2 /f.sub.W                                                                     0.691        0.546  0.775                                          (4) Z.sub.2 /Z.sub.3                                                                       1.186        1.335  1.126                                          (5) |f.sub.2 /f.sub.1 |                                                  0.447        0.418  0.449                                          ______________________________________                                    

FIGS. 3A to 5D respectively show aberrations at the wide angle end, intermediate focal length, and telephoto end in the infinity photographing state according to the first embodiment, and FIGS. 6A to 8D respectively show aberrations at the wide angle end, intermediate focal length, and telephoto end in the extreme close photographing state according to the first embodiment. Also, FIGS. 10A to 12D respectively show aberrations at the wide angle end, intermediate focal length, and telephoto end in the infinity photographing state according to the second embodiment, and FIGS. 13A to 15D respectively show aberrations at the wide angle end, intermediate focal length, and telephoto end in the extreme close photographing state according to the second embodiment. Also, FIGS. 17A to 19D respectively show aberrations at the wide angle end, intermediate focal length, and telephoto end in the infinity photographing state according the third embodiment, and FIGS. 20A to 22D respectively show aberrations at the wide angle end, intermediate focal length, and telephoto end in the extreme close photographing state according to the third embodiment.

In either of the drawings of aberrations, Fno represents an f-number, NA a numerical aperture, Y an image height, d a d-line (λ=587.6 nm), and g a g-line (λ=435.6 nm). In the drawings of astigmatism, each solid line represents a sagittal image surface, and a broken line a meridional image surface, respectively.

From the above-mentioned drawings, it is clearly seen that the aberrations are satisfactorily corrected in each embodiment so as to render an excellent image formation performance.

Further, the fourth to sixth embodiments of the present invention will be explained with reference to the attached drawings.

In either of the drawings, a zoom lens of the present invention which is capable of extreme close photographing is provided with a first lens group G1 having a positive refracting power, a second lens group G2 having a negative refracting power, and a third lens group G3 having a positive refracting power in the named order from the object side. Then, the focal length is changed from a wide angle end to a telephoto end by enlarging an air gap between the first lens group G1 and the second lens group G2 and reducing an air gap between the second lens group G2 and the third lens group G3.

Also, in each of the embodiments, the first lens group G1 is composed of a 1-1 lens group G11 having a negative refracting power and a 1-2 lens group G12 having a positive refracting power in the named order from the object side. Then, focusing from infinity to near is conducted by moving the 1-1 lens group G11 to the object side.

Further, in each of the embodiments, the 1-1 lens group G11 is composed of a front group GF having a positive refracting power and a rear group GR having a negative refracting power in the named order from the object side. Then, the front group GF is composed of a negative meniscus lens being convex on the object side and a biconvex lens in this order from the object side. Also, the rear group GR is composed of a negative lens having a surface with a larger curvature on the image side, a negative lens having a surface with a larger curvature on the object side, and a positive lens having a surface with a larger curvature on the object side, in the named order from the object side.

FIG. 23 is a drawing to show the lens constitution of a zoom lens which is capable of extreme close photographing according to the fourth and fifth embodiments of the present invention.

In the zoom lens shown in FIG. 23, the 1-1 lens group G11 in the first lens group G1 is composed of a front group GF which has a negative meniscus lens being convex on the object side and a biconvex lens, and a rear group GR which has a negative meniscus lens being convex on the object side, a negative meniscus lens being concave on the object side, and a positive meniscus lens being convex on the object side, in the named order from the object side. The 1-2 lens group G12 in the first lens group G1 is composed of a biconvex lens, a compound positive lens of a negative meniscus lens being convex on the object side and a biconvex lens, and a positive meniscus lens being convex on the object side, in the named order from the object side.

Also, the second lens group G2 is composed of a compound negative lens of a biconcave lens and a positive meniscus lens being convex on the object side, and a biconcave lens, in the named order from the object side.

Further, the third lens group G3 is composed of a biconvex lens, a compound positive lens of a biconvex lens, a biconcave lens and a positive meniscus lens being convex on the object side, a biconvex lens, and a negative meniscus lens being concave on the object side, in the named order from the object side.

Note that an aperture stop S is disposed between the second lens group G2 and the third lens group G3, and the aperture stop S is moved integrally with the third lens group G3 during zooming.

FIG. 23 shows a lens layout at the wide angel end, in which the respective lens groups are moved in the directions indicated by the arrows in the drawing during zooming to the telephoto end. That is, the first lens group G1 is fixed, the second lens group G2 is moved to the image side, and the third lens group G3 is moved to the object side when the focal length is changed from the wide angel end to the telephoto end.

Also, as stated above, focusing is effected from infinity to near by moving the 1-1 lens group G11 to the object side.

Fourth Embodiment!

Specific values of the fourth embodiment of the present invention will be shown in the following Table 5. As to the specific values of the total system in Table 5, f represents a focal length, Fno an f-number, and 2ω a field angle, respectively. Also, as to the lens specific values, the first column includes lens surface numbers in the order from the object side, γ in the second column represents a radius of curvature of lens surface, d in the third column a lens surface separation, ν in the fourth column an Abbe's number, and n in the fifth column a refractive index for the d-line (λ=587.6 nm), respectively. Further, as to the lens specific values and the zooming data, B.f. represents a back focus, and TL an axial distance between the surface which is closest to the object side and the image surface, respectively. In addition, as to the zooming data for closest photographing, R represents an axial distance between the object and the image surface, and β a photographing magnification, respectively.

                  TABLE 5                                                          ______________________________________                                         (Total system specific values)                                                 f = 72.10˜105.00˜174.59                                            F.sub.NO = 4.46˜4.98˜5.80                                          2ω = 33.4˜22.9˜13.8°                                  ______________________________________                                         (Lens specific values)                                                               r           d            ν n                                          ______________________________________                                          1    99.3894     2.5000       23.01                                                                               1.86074                                     2    46.6385     3.7000                                                        3    80.5978     8.2000       23.01                                                                               1.86074                                     4    -133.6957   0.1000                                                        5    275.4711    1.8000       54.01                                                                               1.61720                                     6    44.0160     9.9000                                                        7    -47.9935    1.8000       33.89                                                                               1.80384                                     8    -204.3786   0.1000                                                        9    81.0130     3.9000       30.04                                                                               1.69895                                    10    244.6780    (d10 = variable)                                             11    98.8593     4.7000       49.52                                                                               1.74443                                    12    -179.1193   0.1000                                                       13    127.3209    1.8000       25.80                                                                               1.78472                                    14    34.4951     6.9000       60.00                                                                               1.64000                                    15    -651.2001   0.1000                                                       16    72.0354     3.5000       55.60                                                                               1.69680                                    17    260.0235    (d17 = variable)                                             18    -518.6393   1.6000       46.54                                                                               1.80411                                    19    22.2992     5.2000       25.50                                                                               1.80458                                    20    86.4079     2.0000                                                       21    -102.2451   1.6000       46.54                                                                               1.80411                                    22    102.2451    (d22 = variable)                                             23    ∞     1.0000       (aperture stop S)                               24    277.7932    3.4000       55.60                                                                               1.69680                                    25    -76.0460    0.1000                                                       26    29.0602     6.8000       70.41                                                                               1.48749                                    27    -39.2003    1.4000       33.89                                                                               1.80384                                    28    39.2003     4.8000       70.41                                                                               1.48749                                    29    3998.0265   13.4000                                                      30    480.0183    5.3000       27.63                                                                               1.74077                                    31    -43.8032    16.7000                                                      32    -24.1714    1.4000       46.54                                                                               1.80411                                    33    -82.9678    (Bf)                                                         ______________________________________                                         Wide angle        Intermediate                                                                             Telephoto                                          end               position  end                                                ______________________________________                                         (zooming data for infinity photographing)                                      f      72.09930       104.99706 174.58781                                      d10    1.99556        1.99556   1.99556                                        d17    2.07229        8.99829   16.40685                                       d22    40.49327       24.78764  2.72357                                        Bf     51.77942       60.55770  75.21136                                       TL     210.14053      210.13918 210.13734                                      (zooming data for closest photographing)                                       β -0.30977       -0.45111  -0.75009                                       d10    36.79619       36.79619  36.79619                                       d17    2.07229        8.99829   16.40685                                       d22    40.49327       24.78764  2.72357                                        Bf     51.77942       60.55770  75.21136                                       TL     244.94173      244.94014 244.93797                                      R      372.00000      372.00000 372.00000                                      ______________________________________                                         (Condition values)                                                             ______________________________________                                                   fw =      72.099                                                               ft =     174.588                                                               ft' =     88.976                                                               f.sub.11 =                                                                              -90.000                                                               fF =     126.483                                                               R' =     476.818                                                               TL =     210.137                                                               TL' =    233.335                                                               (6) |f.sub.11 |/fw =                                                   1.25                                                                 (7) fF/|f.sub.11 | =                                                   1.41                                                                 (8) R'/ft =                                                                              2.73                                                                 (9) ft'/ft =                                                                             0.51                                                                 (10) TL'/TL =                                                                            1.11                                                       ______________________________________                                    

FIGS. 24A to 29E are drawings to show aberrations in the fourth embodiment, in which FIGS. 24A to 24E are drawings to show the aberrations at a wide angle end in the infinity photographing, FIGS. 25A to 25E are drawings to show the aberrations at an intermediate focal length in the infinity photographing, and FIGS. 26A to 26E are drawings to show the aberrations at a telephoto end in the infinity photographing. On the other hand, FIGS. 27A to 27E are drawings to show the aberrations at the wide angle end in the closest photographing, FIGS. 28A to 28E are drawings to show the aberrations at the intermediate focal length in the closest photographing, and FIGS. 29A to 29E are drawings to show the aberrations at the telephoto end in the closest photographing.

In each of the drawings of aberrations, Fno represents an f-number, NA a numerical aperture, Y an image height, ω a half field angle, A an object height, d a d-line (λ=587.6 nm), and g a g-line (λ=435.8 nm), respectively.

Also, in the drawings of aberrations to show astigmatism, each solid line represents a sagittal image surface, and a broken line a meridional image surface.

From the above-mentioned drawings of aberrations, it is clearly seen that the aberrations are satisfactorily corrected at any object distance and at any focal length in this embodiment so as to secure an excellent image formation performance.

(Fifth Embodiment)

Specific values of the fifth embodiment of the present invention will be shown in the following Table 6. As to the specific values of the total system in Table 6, f represents a focal length, Fno an f-number, and 2ω a field angle, respectively. Also, as to the lens specific values, the first column includes lens surface numbers in the order from the object side, γ in the second column represents a radius of curvature of lens surface, d in the third column a lens surface separation, ν in the fourth column an Abbe's number, and n in the fifth column a refractive index for the d-line (λ=587.6 nm), respectively. Further, as to the lens specific values and the zooming data, Bf represents a back focus, and TL an axial distance between the surface which is closest to the object side and the image surface, respectively. In addition, as to the zooming data for the closest photographing, R represents an axial distance between the object and the image surface, and β a photographing magnification, respectively.

                  TABLE 6                                                          ______________________________________                                         (Total system specific values)                                                 f = 72.10˜105.00˜174.60                                            F.sub.NO = 4.47˜4.99˜5.80                                          2ω = 33.3˜22.9˜13.8°                                  ______________________________________                                                r        d         ν     n                                           ______________________________________                                         (Lens specific values)                                                         1        98.6601    2.5000    26.05  1.78470                                   2        46.1863    3.7000                                                     3        85.2724    8.2000    25.50  1.80458                                   4        -109.4798  0.1000                                                     5        301.6851   1.8000    60.03  1.64000                                   6        47.0000    9.9000                                                     7        -44.4511   1.8000    33.89  1.80384                                   8        -148.8178  0.1000                                                     9        82.7586    3.9000    28.19  1.74000                                   10       185.5582   (d10 = variable)                                           11       80.1395    4.5000    49.45  1.77279                                   12       -230.8690  0.1000                                                     13       131.2066   1.8000    28.19  1.74000                                   14       34.7685    6.9000    82.52  1.49782                                   15       -227.2212  0.1000                                                     16       57.9478    3.5000    60.03  1.64000                                   17       198.8407   (d17 = variable)                                           18       -634.3708  1.6000    49.45  1.77279                                   19       24.1129    4.2000    26.05  1.78470                                   20       77.0897    2.1000                                                     21       -88.6913   1.6000    55.60  1.69680                                   22       88.6913    (d22 = variable)                                           23       ∞    1.0000    (aperture stop S)                                24       208.1505   3.4000    60.03  1.64000                                   25       -75.7259   0.1000                                                     26       28.8092    6.8000    70.41  1.48749                                   27       -38.4094   1.4000    33.89  1.80384                                   28       38.4094    4.8000    70.41  1.48749                                   29       893.9460   13.4000                                                    30       251.6073   4.3000    27.63  1.74077                                   31       -44.6108   16.7000                                                    32       -24.1183   1.4000    45.37  1.79668                                   33       -90.5006   (Bf)                                                       ______________________________________                                                 Wide angle                                                                               Intermediate                                                                               Telephoto                                                end       position    end                                              ______________________________________                                         (Zooming data for infinity photographing)                                      f         72.09930    105.00004   174.60000                                    d10       2.62544     2.62544     2.62544                                      d17       2.14865     9.07345     16.48300                                     d22       40.42375    24.71704    2.65201                                      Bf        52.28636    61.06827    75.72373                                     TL        209.18420   209.18419   209.18418                                    (Zooming data for closest photographing)                                       β    -0.30994    -0.45137    -0.75057                                     d10       37.44552    37.44552    37.44552                                     d17       2.14865     9.07345     16.48300                                     d22       40.42375    24.71704    2.65201                                      Bf        52.28636    61.06827    75.72373                                     TL        244.00428   244.00428   244.00426                                    R         370.00000   370.00000   370.00000                                    (Condition values)                                                             fw = 72.099                                                                    ft = 174.600                                                                   ft' = 88.981                                                                   f.sub.11 = -90.000                                                             fF = 120.868                                                                   R' = 474.951                                                                   TL = 209.184                                                                   TL' = 232.380                                                                  (6) |f.sub.11 |/fw = 1.25                                    (7) fF/|f.sub.11 | = 1.34                                    (8) R'/ft = 2.72                                                               (9) ft'/ft = 0.51                                                              (10) TL'/TL = 1.11                                                             ______________________________________                                    

FIGS. 30A to 35E are drawings to show aberrations in the fifth embodiment, in which FIGS. 30A to 30E are drawings to show the aberrations at a wide angle end in the infinity photographing, FIGS. 31A to 31E are drawings to show the aberrations at an intermediate focal length in the infinity photographing, and FIGS. 32A to 32E are drawings to show the aberrations at a telephoto end in the infinity photographing. On the other hand, FIGS. 33A to 33E are drawings to show the aberrations at the wide angle end in the closest photographing, FIGS. 34A to 34E are drawings to show the aberrations at the intermediate focal length in the closest photographing, and FIGS. 35A to 35E are drawings to show the aberrations at the telephoto end in the closest photographing.

In each of the drawings of aberrations, Fno represents an f-number, NA a numerical aperture, Y an image height, ω a half field angle, A an object height, d a d-line (λ=587.6 nm), and g a g-line (λ=435.8 nm), respectively.

Also, in the drawings of aberrations to show astigmatism, each solid line represents a sagittal image surface, and a broken line a meridional image surface.

From the above-mentioned drawings of aberrations, it is clearly seen that the aberrations are satisfactorily corrected at any object distance and at any focal length in this embodiment so as to secure an excellent image formation performance.

(Sixth Embodiment)

Specific values of the sixth embodiment of the present invention will be shown in the following Table 7. As to the specific values of the total system in Table 7, f represents a focal length, Fno an f-number, and 2ω a field angle, respectively. Also, as to the lens specific values, the first column includes lens surface numbers in the order from the object side, γ in the second column represents a radius of curvature of lens surface, d in the third column a lens surface separation, ν in the fourth column an Abbe's number, and n in the fifth column a refractive index for the d-line (λ=587.6 nm), respectively. Further, as to the lens specific values and the zooming data, Bf represents a back focus, and TL an axial distance between the surface which is closest to the object side and the image surface, respectively. In addition, as to the zooming data for the closest photographing, R represents an axial distance between the object and the image surface, and β a photographing magnification, respectively.

                  TABLE 7                                                          ______________________________________                                          Total System Specific Values!                                                 f = 72.05˜105.00˜174.60                                            F.sub.no = 4.45˜5.01˜5.81                                          2ω = 33.3˜22.8˜13.8°                                  ______________________________________                                                r        d         ν     n                                           ______________________________________                                          Lens Specific Values!                                                         1        89.0624    2.5000    26.05  1.78470                                   2        44.3511    3.6000                                                     3        78.0116    8.2000    25.50  1.80458                                   4        -138.0643  0.1000                                                     5        206.1362   1.8000    60.03  1.64000                                   6        43.1948    10.1000                                                    7        -49.1950   1.8000    33.89  1.80384                                   8        -267.1119  0.1000                                                     9        80.6103    3.7000    28.19  1.74001                                   10       246.9456   (d10 = variable)                                           11       84.8796    4.5000    49.45  1.77278                                   12       -280.3481  0.1000                                                     13       101.6075   1.8000    28.19  1.74000                                   14       34.9930    7.6000    82.52  1.49782                                   15       -238.6230  0.1000                                                     16       72.6182    3.5000    60.03  1.64000                                   17       185.8599   (d17 = variable)                                           18       -1893.6103 1.4000    49.45  1.77278                                   19       30.2490    3.9000    25.50  1.80458                                   20       99.9829    1.8000    0                                                21       -89.5000   1.4000    55.60  1.69680                                   22       89.5000    (d22 = variable)                                           23       ∞    1.0000    (aperture stop S)                                24       147.6900   3.2000    60.03  1.64000                                   25       -67.3328   0.1000                                                     26       29.1657    7.1000    70.41  1.48749                                   27       -38.1350   1.4000    33.89  1.80384                                   28       38.1350    3.1000    70.41  1.48749                                   29       127.1342   15.6000                                                    30       411.4923   3.7000    28.19  1.74000                                   31       -40.2846   15.6500                                                    32       -24.4631   1.4000    45.37  1.79668                                   33       -102.6504  (Bf)                                                       ______________________________________                                                 Wide angle                                                                               Intermediate                                                                               Telephoto                                                end       position    end                                              ______________________________________                                          Zooming data for infinity photographing!                                      f         72.05204    105.00000   174.60000                                    d10       2.63000     2.63000     2.63000                                      d17       2.70000     10.73027    20.52761                                     d22       43.91000    26.44398    2.65425                                      Bf        50.62048    60.05622    74.04862                                     TL        210.11048   210.11048   210.11048                                     Zooming data for extreme close photographing!                                 β    -0.31106    -0.45330    -0.75378                                     d10       37.18051    37.18051    37.18051                                     d17       2.70000     10.73027    20.52761                                     d22       43.91000    26.44398    2.65425                                      Bf        50.62048    60.05622    74.04862                                     TL        244.66099   244.66099   244.66099                                    R         370.00000   370.00000   370.00000                                     Condition values!                                                             fw = 72.052                                                                    ft = 174.600                                                                   ft' = 88.928                                                                   f11 = -89.460                                                                  fF = 129.321                                                                   R' = 475.934                                                                   TL = 210.110                                                                   TL' = 233.029                                                                  (6) |f11|/fW = 1.242                                         (7) fF/|f11| = 1.446                                         (8) R'/ft = 2.726                                                              (9) ft'/ft = 0.509                                                             (10) TL'/TL = 1.109                                                            ______________________________________                                    

FIG. 36 is a drawing to show the lens constitution of a zoom lens which is capable of extreme close photographing according to the sixth embodiment of the present invention.

FIGS. 37A to 42E are drawings to show aberrations in the sixth embodiment, in which FIGS. 37A to 37E are drawings to show the aberrations at a wide angle end in the infinity photographing, FIGS. 38A to 38E are drawings to show the aberrations at an intermediate focal length in the infinity photographing, and FIGS. 39A to 39E are drawings to show the aberrations at a telephoto end in the infinity photographing. On the other hand, FIGS. 40A to 40E are drawings to show the aberrations at the wide angle end in the closest photographing, FIGS. 41A to 41E are drawings to show the aberrations at the intermediate focal length in the closest photographing, and FIGS. 42A to 42E are drawings to show the aberrations at the telephoto end in the closest photographing.

In each of the drawings of aberrations, Fno represents an f-number, NA a numerical aperture, Y an image height, ω a half field angle, A an object height, d a d-line (λ=587.6 nm), and g a g-line (λ=435.8 nm), respectively.

Also, in the drawings of aberrations to show astigmatism, each solid line represents a sagittal image surface, and a broken line a meridional image surface.

From the above-mentioned drawings of aberrations, it is clearly seen that the aberrations are satisfactorily corrected at any object distance and at any focal length in this embodiment so as to secure an excellent image formation performance.

The seventh and eighth embodiments of the present invention will be explained with reference to the attached drawings.

In either of the embodiments, a zoom lens of the present invention is provided with a first lens group G1 having a negative refracting power, a second lens group G2 having a positive refracting power, a third lens group G3 having a negative refracting power, and a fourth lens group G4 having a positive refracting power, in the named order from the object side. Then, the focal length is changed from a wide angle end to a telephoto end by changing an air gap between the first lens group G1 and the second lens group G2, enlarging an air gap between the second lens group G2 and the third lens group G3, and reducing an air gap between the third lens group G3 and the fourth lens group G4. In each of the embodiments, the first lens group G1 is moved to the object side so as to effect focusing from infinity to near.

(Seventh Embodiment)

FIG. 43 is a drawing to show the lens constitution of a zoom lens according to the seventh embodiment of the present invention.

In the zoom lens shown in FIG. 43, the first lens group G1 is composed of a negative meniscus lens being convex on the object side, a biconvex lens, a negative meniscus lens being convex on the object side, a negative meniscus lens being concave on the object side, and a positive meniscus lens being convex on the object side, in the named order from the object.

Also, the second lens group G2 is composed of a biconvex lens, a compound positive lens of a negative meniscus lens being convex on the object side and a positive meniscus lens being convex on the object side, and a positive meniscus lens being convex on the object side, in the named order from the object side.

Further, the third lens group G3 is composed of a compound negative lens of a negative meniscus lens being convex on the object side and a positive meniscus lens being convex on the object side, and a biconcave lens, in the named order from the object side.

Also, the fourth lens group G4 is composed of a biconvex lens, a compound positive lens of a biconvex lens, a biconcave lens, and a positive meniscus lens being convex on the object side, a biconvex lens, and a negative meniscus lens being concave on the object side, in the named order from the object side.

Note that an aperture stop S is disposed between the third lens group G3 and the fourth lens group G4, and the aperture stop S is moved integrally with the fourth lens group G4 during zooming.

FIG. 43 shows a lens layout at the wide angel end, in which the respective lens groups are moved in the directions indicated by the arrows in the drawing when the magnification is changed to the telephoto end. More specifically, the first lens group G1 is fixed during zooming from the wide angel end to the telephoto end, the second lens group G2 is moved to the image side, and then, to the object side, the third lens group G3 is moved to the image side, and the fourth lens group G4 is moved to the object side. Then, a ratio between a movement amount for zooming of the third lens group G3 and that of the fourth lens group G4 is all the time constant during zooming.

Specific values of the seventh embodiment of the present invention will be shown in the following Table 8. As to the specific values of the total system in Table 8, f represents a focal length, Fno an f-number, and 2ω a field angle, respectively. Also, as to the lens specific values, the first column includes lens surface numbers in the order from the object side, γ in the second column represents a radius of curvature of lens surface, d in the third column a lens surface separation, ν in the fourth column an Abbe's number, and n in the fifth column a refractive index for the d-line (λ=587.6 nm), respectively. Further, as to the lens specific values and the zooming data, Bf represents a back focus, and TL an axial distance between the surface which is closest to the object side and the image surface, respectively. In addition, as to the zooming data for the closest photographing, R represents an axial distance (object distance) between the object and the image surface, and β a photographing magnification, respectively.

                  TABLE 8                                                          ______________________________________                                         (Total system specific values)                                                 f = 82.40˜135.00˜194.00                                            F.sub.NO = 4.14˜5.10˜5.73                                          2ω = 28.8˜17.8˜12.5°                                  ______________________________________                                                r        d         ν     n                                           ______________________________________                                         (Lens specific values)                                                         1        89.1784    2.5000    23.01  1.86074                                   2        49.0701    4.1000                                                     3        106.7865   8.1000    23.01  1.86074                                   4        -106.7865  0.5000                                                     5        1559.0379  1.8000    54.01  1.61720                                   6        53.5159    9.6000                                                     7        -45.7095   1.8000    28.56  1.79504                                   8        -171.4311  0.1000                                                     9        100.4498   3.6000    25.80  1.78472                                   10       298.8453   (d10 = variable)                                           11       123.6358   5.0000    52.30  1.74810                                   12       -123.6358  0.1000                                                     13       75.6267    1.8000    25.80  1.78472                                   14       31.3233    7.5000    60.03  1.64000                                   15       284.6918   0.1000                                                     16       70.5329    3.3000    70.41  1.48749                                   17       401.6337   (d17 = variable)                                           18       307.8626   1.6000    46.54  1.80411                                   19       21.1462    5.4006    25.50  1.80458                                   20       60.0066    2.9000                                                     21       -68.4511   1.6000    46.54  1.80411                                   22       179.6301   (d22 = variable)                                           23       ∞    1.0000    (aperture stop S)                                24       163.2350   3.7000    55.60  1.69680                                   25       -91.5164   0.1000                                                     26       27.2830    7.4000    70.41  1.48749                                   27       -44.9905   1.4000    33.89  1.80384                                   28       32.3110    4.9000    70.41  1.48749                                   29       260.2126   15.6000                                                    30       145.3796   5.8000    27.63  1.74077                                   31       -45.9845   14.1000                                                    32       -23.6299   1.4000    46.54  1.80411                                   33       -120.0792  (Bf)                                                       ______________________________________                                                 Wide angle                                                                               Intermediate                                                                               Telephoto                                                end       position    end                                              ______________________________________                                         (Zooming data for infinity photographing)                                      f         82.40000    135.00000   194.00000                                    d10       2.01116     2.90403     2.01106                                      d17       2.05261     6.74308     11.45570                                     d22       40.31604    17.41585    1.74949                                      Bf        51.03263    68.34949    80.19619                                     TL        212.21243   212.21244   212.21244                                    (Zooming data for closest photographing)                                       β    -0.31850    -0.52182    -0.74988                                     d10       40.66459    41.55746    40.66449                                     d17       2.05261     6.74308     11.45570                                     d22       40.31604    17.41585    1.74949                                      Bf        51.03263    68.34949    80.19619                                     TL        250.86586   250.86588   250.66589                                    R         391.90000   391.90000   391.90000                                    (Condition values)                                                             fw = 82.400                                                                    f1 = -100.000                                                                  D.sub.12W = 2.011                                                              Δ1 = 0.000                                                               (11) |f1|/fw = 1.21                                          (12) D.sub.12W /fw = 0.024                                                     (13) Δ1/fw = 0.000                                                       ______________________________________                                    

FIGS. 44A to 49E are drawings to show aberrations in the seventh embodiment, in which FIGS. 44A to 44E are drawings to show the aberrations at a wide angle end in the infinity photographing, FIGS. 45A to 45E are drawings to show the aberrations at an intermediate focal length in the infinity photographing, and FIGS. 46A to 46E are drawings to show the aberrations at a telephoto end in the infinity photographing. On the other hand, FIGS. 47A to 47E are drawings to show the aberrations at the wide angle end in the closest photographing, FIGS. 48A to 48E are drawings to show the aberrations at the intermediate focal length in the closest photographing, and FIGS. 49A to 49E are drawings to show the aberrations at the telephoto end in the closest photographing.

In each of the drawings of aberrations, Fno represents an f-number, NA a numerical aperture, Y an image height, ω a half field angle, A an object height, d a d-line (λ=587.6 nm), and g a g-line (λ=435.8 nm), respectively.

Also, in the drawings of aberrations to show astigmatism, each solid line represents a sagittal image surface, and a broken line a meridional image surface.

From the above-mentioned drawings of aberrations, it is clearly seen that the aberrations are satisfactorily corrected at any object distance and at any focal length in this embodiment so as to secure an excellent image formation performance.

(Eighth Embodiment)

FIG. 50 is a drawing to show the lens constitution of a zoom lens according to the eighth embodiment of the present invention.

In the zoom lens shown in FIG. 50, the first lens group G1 is composed of a negative meniscus lens being convex on the object side, a biconvex lens, a negative meniscus lens being convex on the object side, a negative meniscus lens being concave on the object side, and a positive meniscus lens being convex on the object side, in the named order from the object.

Also, the second lens group G2 is composed of a biconvex lens, a compound positive lens of a negative meniscus lens being convex on the object side and a biconvex lens, and a positive meniscus lens being convex on the object side, in the order from the object side.

Further, the third lens group G3 is composed of a compound negative lens of a negative meniscus lens being convex on the object side and a positive meniscus lens being convex on the object side, and a biconcave lens, in the named order from the object side.

Also, the fourth lens group G4 is composed of a biconvex lens, a compound positive lens of a biconvex lens, a biconcave lens, and a positive meniscus lens being convex on the object side, a biconvex lens, and a biconcave lens, in the named order from the object side.

Note that an aperture stop S is disposed between the third lens group G3 and the fourth lens group G4, and the aperture stop S is moved integrally with the fourth lens group G4 during zooming.

FIG. 50 shows a lens layout at the wide angel end, in which the respective lens groups are moved in the directions indicated by the arrows in the drawing when the focal length is changed to the telephoto end. More specifically, when the focal length is changed from the wide angel end to the telephoto end, the first lens group G1 is moved to the image side, and then, to the object side, the second lens group G2 is fixed, the third lens group G3 is moved to the image side, and the fourth lens group G4 is moved to the object side. Then, a ratio between a movement amount for zooming of the third lens group G3 and that of the fourth lens group G4 is all the time constant during zooming.

Specific values of the eighth embodiment of the present invention will be shown in the following Table 9. As to the specific values of the total system in Table 9, f represents a focal length, Fno an f-number, and 2ω a field angle, respectively. Also, as to the lens specific values, the first column includes lens surface numbers in the order from the object side, γ in the second column represents a radius of curvature of lens surface, d in the third column a lens surface separation, ν in the fourth column an Abbe's number, and n in the fifth column a refractive index for the d-line (λ=587.6 nm), respectively. Further, as to the lens specific values and the zooming data, Bf represents a back focus, and TL an axial distance between the surface which is closest to the object side and the image surface, respectively. In addition, as to the zooming data at the closest photographing, R represents an axial distance (object distance) between the object and the image surface, and β a photographing magnification, respectively.

                  TABLE 9                                                          ______________________________________                                         (Total system specific values)                                                 f = 82.40˜135.00˜194.00                                            F.sub.NO = 4.35˜5.22˜5.81                                          2ω = 29.4˜17.9˜12.5°                                  ______________________________________                                         (Lens specific values)                                                               r           d             ν n                                         ______________________________________                                          1    95.6946     2.5000        23.01                                                                               1.86074                                    2    52.2106     4.4000                                                        3    123.9374    7.4000        23.01                                                                               1.86074                                    4    -123.9374   2.5000                                                        5    1338.4617   1.8000        54.01                                                                               1.61720                                    6    55.4141     9.5000                                                        7    -49.5438    1.8000        33.89                                                                               1.80384                                    8    -202.7933   0.1000                                                        9    111.6994    4.0000        30.04                                                                               1.69895                                   10    2627.6977   (d10 = variable)                                             11    192.3418    4.5000        52.30                                                                               1.74810                                   12    -192.3418   0.1000                                                       13    146.3540    1.8000        25.80                                                                               1.78472                                   14    50.8330     6.4000        60.03                                                                               1.64000                                   15    -20243.6100 0.1000                                                       16    64.9750     4.1000        70.41                                                                               1.48749                                   17    137.1326    (d17 = variable)                                             18    63.6793     1.6000        46.54                                                                               1.80411                                   19    31.2961     4.5000        25.50                                                                               1.80458                                   20    64.8973     2.9000                                                       21    -151.6662   1.6000        46.54                                                                               1.80410                                   22    78.5544     (d22 = variable)                                             23    ∞     1.0000        (aperture stop S)                              24    80.4808     4.5000        55.60                                                                               1.69680                                   25    -80.4808    0.1000                                                       26    29.2569     11.8000       70.41                                                                               1.48749                                   27    -52.5326    1.4000        33.89                                                                               1.80384                                   28    23.3810     4.5000        70.41                                                                               1.48749                                   29    50.6888     15.4000                                                      30    121.1895    6.4000        27.63                                                                               1.74077                                   31    -35.5712    5.2000                                                       32    -29.7009    1.4000        46.54                                                                               1.80411                                   33    231.2567    (Bf)                                                         ______________________________________                                         Wide angle        Intermediate                                                                             Telephoto                                          end               position  end                                                ______________________________________                                         (zooming data for infinity photographing)                                      f      82.39960       135.00002 193.99997                                      d10    1.99577        0.82666   1.99584                                        d17    2.00099        18.55398  30.93451                                       d22    58.59474       26.40580  2.33063                                        Bf     54.01785       69.65380  81.34843                                       TL     229.90934      228.74023 229.90940                                      (zooming data for closest photographing)                                       β -0.31863       -0.51926  -0.75016                                       d10    40.66407       39.29069  40.66415                                       d17    2.00099        18.55398  30.93451                                       d22    58.59474       26.40580  2.33063                                        Bf     54.01784       69.65379  81.34843                                       TL     268.57764      267.20426 268.57771                                      R      408.80000      408.80000 408.80000                                      ______________________________________                                         (Condition values)                                                             ______________________________________                                                  fw =      82.400                                                               f1 =     -100.000                                                              D.sub.12W =                                                                               1.996                                                               Δ1 =                                                                                1.600                                                               (11) |f1|/fw =                                                          1.21                                                                (12) D.sub.12W /fw =                                                                      0.024                                                               (13) Δ1/fw =                                                                        0.019                                                      ______________________________________                                    

FIGS. 51A to 56E are drawings to show aberrations in the eighth embodiment, in which FIGS. 51A to 51E are drawings to show the aberrations at a wide angle end in the infinity photographing, FIGS. 52A to 52E are drawings to show the aberrations at an intermediate focal length in the infinity photographing, and FIGS. 53A to 53E are drawings to show the aberrations at a telephoto end in the infinity photographing. On the other hand, FIGS. 54A to 54E are drawings to show the aberrations at the wide angle end in the closest photographing, FIGS. 55A to 55E are drawings to show the aberrations at the intermediate focal length in the closest photographing, and FIGS. 56A to 56E are drawings to show the aberrations at the telephoto end in the closest photographing.

In each of the drawings of aberrations, Fno represents an f-number, NA a numerical aperture, Y an image height, ω a half field angle, A an object height, d a d-line (λ=587.6 nm), and g a g-line (λ=435.8 nm), respectively.

Also, in the drawings of aberrations to show astigmatism, each solid line represents a sagittal image surface, and a broken line a meridional image surface.

From the above-mentioned drawings of aberrations, it is clearly seen that the aberrations are satisfactorily corrected at any object distance and at any focal length in this embodiment so as to secure an excellent image formation performance.

According to the present invention, it is possible to provide a zoom lens suitable for a single lens reflex camera, which is capable of zooming at any object distance from infinity to near, without any deviation of the image plane in zooming at any object distance, and is capable of obtaining the maximum image magnification about -0.75 to -1 or around, has a zoom ratio of about 2 or more, and has an excellent image formation performance and a sufficient amount of light at marginal area in any photographing condition.

According to the present invention, it is also possible to realize a zoom lens capable of extreme close photographing and suitable for a single lens reflect camera, which zoom lens is capable of changing the focal length at any object distance from infinity to near, is capable of securing the maximum image magnification of about -0.75, and has an excellent image formation performance and a sufficient amount of light at marginal area in any object distance.

Further, according to the present invention, it is possible to realize a zoom lens suitable for a single lens reflex camera, which is capable of zooming at any object distance from infinity to near as about double the focal length at the telephoto end in the infinity photographing state, is capable of securing the maximum image magnification of about -0.75, and has an excellent image formation performance and a sufficient amount of light at marginal area in any object distance. 

What is claimed is:
 1. A zoom lens comprising a first lens group having a positive refracting power, a second lens group having a negative refracting power, and a third lens group having a positive refracting power, disposed in the named order from an object side:wherein said first lens group has a first sub-group having a negative refracting power and a second sub-group having a positive refracting power, disposed in the named order from the object side; wherein zooming from a wide angle end to a telephoto end is effected by increasing a gap between said first lens group and said second lens group and reducing a gap between said second lens group and said third lens group, while fixing said first lens group; wherein focusing from infinity distance object to near distance object is effected by moving said first sub-group to the object side; and wherein the following condition is satisfied:

    0.5<f1/fw<2.0,

where fw is a focal length of a total system when an object at infinity is in focus at the wide angle end; and f1 is a focal length of said first lens group when the object at infinity is in focus.
 2. A zoom lens according to claim 1, wherein the following condition is satisfied:

    0.5<|f.sub.1-1 /fw|<2.0,

where f₁₋₁ is a focal length of said first sub-group.
 3. A zoom lens according to claim 1, wherein the following condition is satisfied:

    0.25<f.sub.1-2 /fw<1.5,

where f₁₋₂ is a focal length of said second-group.
 4. A zoom lens according to claim 1, wherein the following condition is satisfied:

    0.6<Z2/Z3<2.0,

where Z2 is β2T/β2W; Z3 is β3T/β3W; β2T is an image magnification of said second lens group at the telephoto end; β2W is an image magnification of said second lens group at the wide angle end; β3T is an image magnification of said third lens group at the telephoto end; and β3w is an image magnification of said third lens group at the wide angle end.
 5. A zoom lens according to claim 1, wherein the following condition is satisfied:

    0.25<|f2/f1|<0.7,

where f2 is a focal length of said second lens group.
 6. A zoom lens according to claim 1, wherein the position of said third lens group at the telephoto end is closer to the object that at the wide angle end.
 7. A zoom lens comprising a first lens group having a positive refracting power, a second lens group having a negative refracting power, and a third lens group having a positive refracting power, disposed in the named order from an object side:wherein said first lens group has a first sub-group having a negative refracting power and a second sub-group having a positive refracting power, disposed in the named order from the object side; wherein zooming from a wide angle end to a telephoto end is effected by increasing a gap between said first lens group and said second lens group and reducing a gap between said second lens group and said third lens group while fixing said first lens group; wherein focusing from infinity to near distance is effected by moving said first sub-group to the object side; wherein when a focal length of a total system when at an object at infinity is in focus at the wide angle end is fw and a focal length of said first lens group when the object at infinity is in focus is f1, the following condition is satisfied:

    0.5<f1/fw<2.0;

wherein when a focal length of said first sub-group is f₁₋₁, the following condition is satisfied:

    0.5<|f.sub.1-1 /fw|<2.0;

wherein when a focal length of said second sub-group is f₁₋₂, the following condition is satisfied:

    0.25<f.sub.1-2 /fw<1.5;

wherein when Z2 is β2T/β2W, Z3 is β3T/β3W, an image magnification of said second lens group at the telephoto end is β2T, an image magnification of said second lens group at the wide angle end is β2W, an image magnification of said third lens group at the telephoto end is β3T, and an image magnification of said third lens group at the wide angle end is β3w, the following condition is satisfied:

    0.6<Z2/Z3<2.0;

and wherein when a focal length of said second lens group is f₂, the following condition is satisfied:

    0.25<|f2/f1|<0.7.


8. A zoom lens according to claim 7, wherein the position of said third lens group at the telephoto end is closer to the object than that at the wide angle end.
 9. A zoom lens capable of extreme close photographing, comprising a first lens group having a positive refracting power and at least two lens groups disposed on an image side of said first lens group:wherein a focal length of a total lens system is changed by changing at least two air gaps between said lens groups; wherein said first lens group has a first sub-group having a negative refracting power and a second sub-group having a positive refracting power, disposed in the named order from the object side; wherein a focusing from infinity distance object to near distance object is effected by moving said first sub-group to the object side; and wherein when a focal length of said first sub-group is f11 and a focal length of the total lens system in an infinity in-focus state at the wide angle end is fw, the following condition is satisfied:

    0.8<|f11|/fw<1.6.


10. A zoom lens capable of extreme close photographing according to claim 9,wherein said first sub-group comprises a front group having a positive refracting power and a rear group having a negative refracting power, disposed in the named order from the object side; and wherein when a focal length of said front group is fF and a focal length of said first sub-group is f11, the following condition is satisfied:

    0.9<fF/|f11|<1.9.


11. A zoom lens capable of extreme close photographing according to claim 10, wherein said front group has a negative meniscus lens being convex on the object side and a biconvex lens, disposed in the named order from the object side.
 12. A zoom lens capable of extreme close photographing according to claim 11, wherein said rear group GR comprises a negative lens having a surface with a larger curvature on the image side, a negative lens having a surface with a larger curvature on the object side, and a positive lens having a surface with a larger curvature on the object side disposed in the named order from the object side.
 13. A zoom lens capable of extreme close photographing according to claim 9, wherein when an axial distance between an object in a state of an image magnification being -0.5 at the telephoto end and an image surface is R', a focal length of the lens total system in an infinity in-focus state at the telephoto end is ft, and a focal length of the lens total system in the state of the image magnification being -0.5 at the telephoto end is ft', the following condition is satisfied:

    R'/ft<4,

and

    ft'/ft<0.7.


14. A zoom lens capable of extreme close photographing according to claim 9, wherein when an axial distance between a surface closest to the object side in an infinity in-focus state at the telephoto end and the image surface is TL, and an axial distance between a surface closest to the object side in a state of the image magnification being -0.5 at the telephoto end and the image surface is TL', the following condition is satisfied:

    1.05<TL'/TL<1.4.


15. A zoom lens capable of extreme close photographing, comprising a first lens group having a positive refracting power and at least two lens groups disposed on an image side of said first lens group:wherein a focal length of a total lens system is changed by changing at least two air gaps between said lens groups; wherein said first lens group has a first sub-group having a negative refracting power and a second sub-group having a positive refracting power, disposed in the named order from the object side; wherein a focusing from an object at infinity to an object at a close distance is effected by moving said first sub-group to the object side; wherein when a focal length of said first lens group is f11 and a focal length of the total lens system in an infinity in-focus state at the wide angle end is fw, the following condition is satisfied:

    0.8<|f11|/fw<1.6;

wherein when an axial distance between an object in a state of an image magnification being -0.5 at the telephoto end and an image surface is R', a focal length of the lens total system in an infinity in-focus state at the telephoto end is ft, and a focal length of the lens total system in the state of the image magnification being -0.5 at the telephoto end is ft', the following condition is satisfied:

    R'/ft<4,

and

    ft'/ft<0.7;

and wherein when an axial distance between a surface closest to the object side in an infinity in-focus state at the telephoto end and the image surface is TL, and an axial distance between a surface closest to the object side in the state of the image magnification of -0.5 at the telephoto end and the image surface is TL', the following condition is satisfied:

    1.05<TL'/TL<1.4.


16. A zoom lens capable of extreme close photographing according to claim 15:wherein said first sub-group comprises a front group having a positive refracting power and a rear group having a negative refracting power, disposed in the named order from the object side; and wherein when a focal length of said front group is fF and a focal length of said first sub-group is f11, the following condition is satisfied:
 0. 9<fF/|f11|<1.9;wherein said front group GF has a negative meniscus lens being convex on the object side and a biconvex lens, disposed in the named order from the object side; and wherein said rear group comprises a negative lens having a surface with a larger curvature on the image side, a negative lens having a surface with a larger curvature on the object side, and a positive lens having a surface with a larger curvature on the object side, disposed in the named order from the object side. 